The subject matter disclosed herein relates to thermal response of turbine wheels, and more particularly to a split impeller configuration on adjacent turbine wheels for synchronizing thermal response of the adjacent wheels.
FIG. 1 illustrates a prior art turbomachine 1. In the turbomachine 1, adjacent wheels 2, 3 on a compressor rotor 8 include a rabbet joint 4 between the wheels 2, 3. The rabbet joint 4 can crack due to high crushing stresses experienced during start up of the turbomachine 1. Studies of the cracking problem indicate that difference in thermal response of the two wheels 2, 3 is a significant contributor to high crushing stress. Thermal response of a given wheel is indicated by its bulk temperature variation during a transient. The difference in thermal response is represented by difference in bulk temperature of the two wheels 2, 3. A current impeller 5 is machined entirely on the wheel 2 and thereby wheel 2 heats up quicker than wheel 3. As a consequence, male portion 6 of the rabbet joint 4 heats up quicker than the female portion 7 of the rabbet joint 4. The difference in rates of heating causes high rabbet loads and thereby high crushing stress on the rabbet joint 4, which can lead to cracking. It is appreciated that the heat transfer area for the wheel 2 is greater than the heat transfer area for the wheel 3.